ffmpeg -i tmp1.mp4 -vcodec copy -acodec copy -vbsf h264_mp4toannexb tmpp1.ts

ffmpeg -i tmp2.mp4 -vcodec copy -acodec copy -vbsf h264_mp4toannexb tmpp2.ts

ffmpeg -i "concat:tmpp1.ts|tmpp2.ts" -acodec copy -vcodec copy -absf aac_adtstoasc tmp.mp4
del /f /q tmpp1.ts
del /f /q tmpp2.ts
pause>nul